Coupling



FIG. 1 is a side elevational view of a coupling showing my design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a front perspective view thereof;

FIG. 4 is a side elevational view of my new design, the sole difference being in the position of the coupling;

FIG. 5 is a front perspective view of my design, the sole difference being in the position of the coupling; and,

FIG. 6 is a rear perspective view of my design, the sole difference being in the position of the coupling. 

The ornamental design for a coupling, as shown and described. 